نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال چهل و چهارم شماره 4 (پیاپی 77، زمستان 1393)

Pavement foundation layers play a crucial role in construction and in-service loads. Unbound subbase as a layer of foundation can be constructed by natural and recycled materials. Over last two decades, sustainable development has been a prominent issue in all infrastructures and need for sustainable highway design, construction, maintenance and rehabilitation is becoming a priority for companies which work in highway industry. Each year, millions of tonnes of construction waste are produced from old buildings demolishing, poor drainage kerbs and pavement blocks renewal works, redesign or reconstruction of structures in Iran, which are carried to landfills placed outside the cities. The analysis of cost for demolishing, equipments and machineries, transportation and stockpiling showed that a huge cost is enforced on the government construction budget [1]. Dwindling number of landfills, diminishing of natural resources, increasing costs of extraction in quarries and transporting to the required projects on the one hand and adverse environmental impacts of the extraction and disposal on the other hand persuade a developing country such as Iran to take essential steps for recycling the construction and demolition wastes.

Construction of submerged groynes is one of the newest methods in beach stabilization. Practical knowledge of the submerged groynes design and their effects on the wave, current and shoreline change is not enough and it is developing. So far, numerous researches have been conducted for better understanding of wave’s pattern on the groynes. However, studies of the submerged groynes in a coastal area, has received little attention. Since the problem of coastal stabilization is of high importance, there is a need for more research in this area. Therefore, the access to wave parameters using numerical modeling can provide useful information for the design and layout of groynes, environmental considerations, and the main factors. In this study, a numerical simulation model of the waves by Mike 21 around the submerged groynes and comparison with the non submerged groynes is performed and variation of height of the waves around the groynes is discussed. Also, the main objective of this study has been focused on the groyne crest height impact on wave heights.

With respect to catastrophic effects of apossible failure of concrete dam, theircontinuous safety evaluation seems essential. Investigation on concrete dams has increased extensively during the recent decades. However, considering intrinsic complexity of arch dams, there are considerable ambiguities that require more attention. One of the existing concerns is nonlinear dynamic behavior analysis of dam subject to sever loading such as earthquakes at MCL. On the other hands type of earthquake have different effects on seismic behavior of dam. Near-filed and far-field type of earthquake are two major classifications of earthquakes. The importance of the near source motion characteristics on the elastic and inelastic behavior of engineered structures has been noted by several researchers [1, 2]. Various criteria for classification of earthquakes to near-and far-field types have also been proposed [2].

When a structure is placed on an erodible bed, it causes an increase in local sediment transport capacity and consequently this leads to scour in the vicinity of the structure. This is referred to as local scour in the literature. Local scour has been identified as one of the key factors that cause failure of structures in the bridges, jetties and offshore platforms. The complexities of bridge scour mechanism have caused the scour to be one of the most active topics in civil engineering researches. Numerous studies have been reported on local scour around bridge piers in steady currents in the last decades. A majority of these studies deal with laboratory model studies. A brief literature review can reveal the importance of this subject. Several methods have been proposed by researchers to control the scour around the bridge piers. These methods can be divided into two main categories: the first one is the armoring method or increasing the resistance of the bed material around the pier as rip rap, and the second one is altering of the flow pattern around the pier.

Groundwater resources are one of the main sources of water supply. In recent years, the natural balance between fresh and saline water due to over-exploitation has been deteriorated and groundwater levels GLs in many parts of the country aquifers have turned negative. Evaluation and prediction of groundwater levels through specific models helps in forecasting of groundwater resources. In recent years, artificial neural networks (ANNs) have been used for GL prediction, aquifer parameter determination and groundwater quality monitoring. An important feature of ANN models is their ability to detect patterns in a complex system. Yang et al. [1] evaluated the potential of a BPANN and an Integrated Time Series (ITS) model based on the modern statistical models and techniques for the purpose of predicting the GL in an arid and semi-arid region of China. However, ANNs and other linear and non-linear methods frequently used have limitations with non-stationary data. ANN models cannot handle non-stationary data without input data pre-processing. The methods for dealing with non-stationary data are not as advanced as those for stationary data and additional research is needed to investigate methods that are better able to handle non-stationary data effectively. An example of such a method is wavelet analysis. Wavelet analysis can be used to decompose an observed time series (such as GL) into various components so that the new time series can be used as inputs for an ANN model. In this research, WA–ANN models were developed and compared with ANN and MLR models for forecasting GL at two tubes observed wells in the Sharif Abad watershed in Qom, Iran. In this paper, a new method based on coupling discrete wavelet transforms (WA) and ANN for GL forecasting is proposed. The relative performance of the proposed coupled wavelet-ANN models was compared to regular ANN models and Multiple Linear Regression (MLR) models for monthly GL forecasting. The comparison of the prediction accuracies of the WA-ANN and other models indicated that the proposed WA-ANN model could predict GL time series because of using multi-scale time series data as the ANN input layer.

The use of the cylindrical structures has some advantages such as low cost, simple design, easy construction and the higher discharge coefficient. Masoudian and Gharahgezlou [1] performed several experiments on free over flow on a cylindrical weir to determine the discharge coefficient (Cd) and found that the Cd raises with increasing the nondimensional ratios of [Hw/R], in which R: cylinder radius, [Hw/yup] and non-dimensional numbers of Re and We. Masoudian et al. [2] performed a laboratory study on geometric and hydraulic parameters effect on the flow through the cylindrical weir that demonstrates with increasing the dimensionless ratio of [yup/D] and [yup/a], Cd goes up. They indicate that for a constant value of [yup/D] ratio, the Cd decreases with the increasing gate opening height as well as, cylindrical gate discharge coefficient is more than a sliding gate discharge coefficient [2]. Along with the vertical movement of cylindrical weir-gate, three different flows of over flow on weir, combined flow thought the weir-gate and under flow the gate can be observed. As a result, discharge coefficient of combined flow and the energy loss will also change. This structure can be used for precise control and measurement of passing flow in the low and high water levels for instant during the drought or flood conditions, therefore, in present research, an experimental study on the effect of vertical movement of cylindrical weir gate on flow hydraulics was performed.

Concentric steel X-braced frames are commonly used in steel structures to resist the lateral forces due to wind or earthquake loads. Common assumption for the brace connection is pinned, but in practice the connection of the braces could have partial rigidity, with regard to the details of the connection. In modeling of the X-braced frames, it is assumed that the diagonals at mid-span are crossing without interrupting each other; while, in practice one of the diagonals is discontinuous. On the other hand, the buckling load of the braces is affected by the effective length factor that is affected by the conditions of the end and mid connections [1, 2]. Therefore, changing the conditions of the brace connections affects the buckling load of the brace and consequently the behavior of the frame. In this paper, the behavior of two dimensional X-braced steel frames with different number of stories (3, 5 and 10) and bays (3 and 5) was investigated which were different in connection conditions of braces. The end and midconnections of the braces were modeled in either pinned or rigid extreme states with proportional effective length factors.

The seismic rehabilitation of exsisting buildings is a key issue in seismic zones. In fact, moderate to strong earthquakes are threatening the lives of many people and inflict severe damages on structures and infrastructures, so that they put a stop to daily life and cause the economy suffer from downturn in regional scale [1, 2]. Hence, extensive researches on the evaluation of seismic performance of the steel moment frames have been carried out in recent years [3]. Ghodrati et al. studied ordinary steel moment frame buildings designed by Code 2800 (second edition) [4] based on the Seismic Retrofitting Provisions [5] and came to the conclusion that buildings with moderate-to-high hieghts need retrofitting in the base upgrading level when using nonlinear static method to control [6, 7]. They also concluded that all buildings do not satisfy the base upgrading level when the spectral dynamic method is employed to control the accuracy of the design. In this study, it is intended to investigate and employ the most appropriate method in order to rehabilitate steel buildings in a way that not only it shows the real performance of the structure, but also it has the lowest cost.2.1. Studied models The plan for designated sample buildings is a 15*15m square with frames that are 5 meters away from each other. The studied buildings were selected in four types concerning the height: two, four, six and eight-story in which the height of each story was 3m. The buildings were assumed residential types with intermediate importance in the south of Tehran. The ground type was selected IV. In all buildings, the resistant system against the lateral loads in both directions has been steel ordinary moment frame. In order to bear the gravity load of stories, the oneway slab system (rib and block) has been used in ceiling. The connections are assumed to be rigid. Due to the type of selected plan and the direction of ribs, all of the frames in buildings have almost similar situations, and the required conclusions for the whole building can be reached through studying one frame. In all of these buildings, the frame being studied is the frame of axis-2 (a middle frame) that has more critical state due to the loading, especially in the columns. Fig. 1 shows the plan of buildings under the consideration and the frame being studied. Previous researches showed that ordinary steel moment frame buildings which have been designed according to the Code 2800 (2nd edition), in controlling through the some methods of Seismic Retrofitting Provisions were not accepted and they need to be improved [6, 7]. In the present study, it is intended to investigate and identify the most appropriate method in order to rehabilitate such buildings in a way that it shows the real performance of the structure, meanwhile, it has the lowest cost. To this end, after rehabilitating of the members using different analyses in Seismic Retrofitting Provisions, the weights of structures and new members are calculated and compared with their previous weights, and overweight percentage, due to rehabilitating, is obtained. Fig. 2 shows the overweight percentage diagram of rehabilitated buildings in different methods.

Air pollutants are potentially hazardous to human health, plants, animals, materials and surrounding environment including building, roads, etc. Almost in all cases, it is the human activities that are the main sources of pollution. Air pollution modelling is an essential tool for air pollution studies. Considering that observations are often sparse, models can be used to make inferences on concentrations where there is no information [1, 2]. The current study aimed to consider the pollutants (CO and SO2) concentration in areas adjacent to Tabriz Oil Refining Company and comparison of concentration with clean air standards of Environmental Organization of Iran. The effect of wind speed and direction on dispersion profile of air pollution was also considered. Therefore, the ISCST (Industrial Source Complex-Short Term) model was used to simulate pollutant distributions on two different days in order to assess the ground level concentration of pollutant in the study area.

Eutrophication is one of the most important environmental problems of the enrichment in surface freshwater bodies due to organic compounds originating from agricultural activities and industrial effluents. Eutrophication causes the reduction of water quality in eutrophic lakes and reservoirs. The purpose of this study was two dimensional simulation of eutrophication in Mahabad Reservoir by using of CE-QUAL-W2 model. Eutrophication is a process that forms due to excessive accumulation of nutrients in the body of water in the reservoir or lake sediments. It can lead to the activity of microorganisms and be followed by the uncontrolled growth of aquatic plants [1]. One of the important studies on the use of CE-QUAL-W2 model in the reservoir can be mentioned by choi et al. [2]. They used this model for the investigation of possible impacts of enlarged water body according to dam reconstruction on the hydrodynamics and water quality of the reservoir. For calibration and validation of the model, field-collected data were compared with model predictions for water level fluctuations and water temperature and the model results showed a good agreement with field measurements. Demand for water is steadily increasing throughout the world. Water quality has become increasingly more important in reservoir management. Reservoir managers and the public have come to the realization that water quality affects other environmental interests, such as fish and wildlife, and can impact or impair water use. The Mahabad dam has great importance in the supply of drinking water in Mahabad city. Inthe present research, changes of water quality in this reservoir were studied and provide an appropriate model to simulation of eutrophication in Mahabad Reservoir.